Conveyor assembly

ABSTRACT

A conveyor assembly for xerographic reproducing machines. The conveyor assembly includes a plurality of elongated buckets mounted at their opposite ends to endless belts. The belts are each mounted on upper and lower pulleys mounted on shafts. The lowermost shaft is an idler while the uppermost shaft is power driven to move the buckets in a continuous path of movement from a developer sump portion whereat two-component developer is picked up by the buckets to above the upper pulleys. There the buckets are inverted by their movement to dump the conveyed developer to an input chute leading to the upper end of a cascade development zone. A closed cell polyurethane foam roller of a diameter substantially equal to that of the upper pulleys is mounted therebetween for rotation therewith whereby developer being spilled by the buckets may be directed to the input chute.

United States Patent Britt et a1.

[54] CONVEYOR ASSEMBLY [72] Inventors: James E. Britt, Penfield; Robert E.

Hewitt, Ontario, both of N.Y.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

22 Filed: Jan. 6, 1971 21 Appl.No.:104,34l

[56] References Cited UNITED STATES PATENTS 10/1896 Slattery ..198/l40 12/1896 Ream ..l98/140X lllllll 9 I mlllnm s [4 1 Aug. 29, 1972 Primary Examiner-Edward A. Sroka AttorneyJames J. Ralabate, Norman E. Schrader and Michael J. Colitz, Jr

[5 7] ABSTRACT A conveyor assembly for xerographic reproducing machines. The conveyor assembly includes a plurality of elongated buckets mounted at their opposite ends to endless belts. The belts are each mounted on upper and lower pulleys mounted on shafts. The lowermost shaft is an idler while the uppermost shaft is power driven to move the buckets in a continuous path of movement from a developer sump portion whereat two-component developer is picked up by the buckets to above the upper pulleys. There the buckets are inverted by their movement to dump the conveyed developer to an input chute leading to the upper end of a cascade development zone. A closed cell polyurethane foam roller of a diameter substantially equal to that of the upper pulleys is mounted therebetween for rotation therewith whereby developer being spilled by the buckets may be directed to the input chute.

3 Claims, 2 Drawing Figures PATENTEDwszs I972 SHEET 1 0F 2 INVENTORS JAMES E. BRITT ROBERT E. HEWITT BY V c t ATTORNEY PATENTEDmcza m2 SHEET 2 [IF 2 FIG. 2

CONVEYOR ASSEMBLY This invention relates to a conveyor assembly which is well suited for use in conveying developer from a sump to an entrance chute leading to the top of a cascade development zone. More specifically, this invention relates to the use of a closed cell polyurethane roller mounted between pulleys which direct bucket conveyors in a path of movement, the roller functioning to assist in directing the conveyed developer toward the input chute.

In the process of xerography, as described for example in US. Pat. No. 2,297,691 to Chester F. Carlson, a xerographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support latent electrostatic images. In the usual manner of carrying out the process, the xerographic surface is electrostatically charged uniformly over its surface and then exposed to a light pattern of the image being reproduced to thereby discharge the charge to the areas where light strikes the layer. The undischarged areas of the layer thus form an electrostatic charge pattern in conformity with the configuration of the original light pattern.

The latent electrostatic image can then be developed by contacting it with a finely divided electrostatically attractable material, such as, a powder. The powder is held in image areas by the electrostatic charges on the layer. Where the charge field is greatest, the greatest amount of material is deposited. Where the charge field is least, little or no material is deposited. Thus, a powder image is produced in conformity with a light image of copy being reproduced. The powder is subsequently transferred to a sheet of paper or other surface and suitably affixed thereto to form a permanent print.

In order to effect efficient cascade development of latent electrostatic images on the photoreceptive member, bucket conveyor assemblies have traditionally been employed to lift the developer from a sump area beneath the cascade zone to an area thereabove so that it may be poured under the influence of gravity across the image to be developed. The cascaded or gravity dropped developer is recollected in the sump for being reconveyed to the top of the development zone by a bucket conveyor assembly.

Such bucket conveyor assemblies have been traditionally constructed of a series of elongated buckets mounted transversely with respect to their direction of movement with their opposite ends secured to endless chains or belts. The chains or belts are then mounted on upper and lower sets of sprockets or pulleys which may then be power driven to afiect the movement of the buckets from a loading position in the sump to a discharge position above guide chutes leading to the top of the cascade development zone. I

Such systems have been generally found sufficiently efficient to preclude modifications thereto. An advantage of this type of arrangement is that as the loaded buckets begin to move across the uppermost pulley, quantities of developer will be spilled therefrom and drop between the uppermost pulleys back to the sump causing an intermixing of the developer. While such is a desirable end, it does, in fact, have the disadvantage of reducing the overall conveying efiiciency in that substantially less than the total amount of conveyed developer is actually deposited on the chute and into the cascade zone.

It is therefore an object of the instant invention to increase the efficiency of conveyor assemblies of the type wherein buckets transport particulate material to an elevated location.

It is a further object of the instant invention to transport developer material from the sump portion to an elevated location in an efficient manner.

It is a further object of the instant invention to direct substantially all developer material conveyed by a bucket conveyor assembly into developer input chutes adjacent the uppermost portion of a cascade development zone.

It is a further object of the instant invention to fill the space between the upper pulley members of a bucket conveyor assembly of a cascade development system to thereby increase the conveying efficiency of the assemblies.

These and other objects of the instant invention are attained by a conveyor assembly for xerographic reproducing machines. The conveyor assembly includes a plurality of elongated buckets mounted at their opposite ends to endless belts. The belts are each mounted on upper and lower pulleys mounted on shafts. One shaft is an idler while the other is power driven to move the buckets in a continuous path of movement from a developer sump portion to above the upper pulleys. The buckets are inverted by their movement to dump conveyed developer to an input chute leading to the upper'end of a cascade development zone. A closed cell polyurethane foam roller of a diameter substantially equal to that of the upper pulleys is mounted therebetween for rotation therewith whereby developer being spilled by the buckets may be directed to the input chute.

For a better understanding of the present invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic side elevation of a continuous automatic xerographic reproducing machine having a cascade development zone and a bucket conveyor assembly constructed in accordance with the instant invention and FIG. 2 is an enlarged perspective view of the bucket conveyor assembly as shown in FIG. 1.

Referring now to the drawings, there is shown in FIG. 1 an embodiment of the subject invention in a suitable environment such as an automatic xerographic reproducing machine. The automatic xerographic reproducing machine includes a xerographic plate or surface 10 formed in the shape of a drum. The plate has a photoconductive layer or light receiving surface on a conductive backing, joumaled on shaft 12 in a frame to rotate in the direction indicated by the arrow by power source MOT-l. The rotation will cause the plate surface to sequentially pass a series of xerographic processing stations. For the purposes of the present disclosure, the several xerographic processing stations in the path of movement of the plate surface may be described functionally as follows:

A charging station A, at which a uniform electrostatic charge is deposited on the photoconductive plate;

An exposure station B, at which light or radiation pattern of copy to be reproduced is projected onto the plate surface to dissipate the charge in the exposed areas thereof to thereby form a latent electrostatic image of the copy to be reproduced;

A developing station C at which xerographic developing material, including toner particles having an electrostatic charge opposite to that of the latent electrostatic image, is cascaded over the plate surface whereby the toner particles adhere to the latent electrostatic image to form a toner-powder image in a configuration of the copy being reproduced;

A transfer station D at which the toner-powder image is electrostatically transferred from the plate surface to a transfer material or a support surface; and

A drum cleaning and discharge station E at which the plate surface is brushed to remove residual toner particles remaining thereon after image transfer and exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

The conveyor assembly 14 for transporting the developer material from the sump 16 to the elevated location 18 is seen more particularly in FIG. 2. The assembly includes a plurality of buckets 20 stapled or otherwise suitably secured to endless belts 22 mounted on upper pulleys 24 and lower pulleys 26 for movement in the .path of travel as indicated by the arrow. The lowermost pulleys are located so that the buckets can pass through a sump of developer material beneath the cascade development zone 28. The sump is continually reloaded with developer falling from the cascade development zone and captured and directed by pickoff baffle 30.

Above the development zone is an input chute 32 receiving the conveyed developer as it is dumped from the buckets and gravity dropped thereto for cascading through the development zone.

Due to the fact that toner particles are lost from the development system through the development of images on the xerographic drum, a toner dispenser 36 is employed to supplement that toner lost from the system due to normal operations.

The pulley members are each fixedly mounted on horizontal shafts 38 and 40 parallel to each other as well as parallel to the axis of rotation of the xerographic drum. The lowermost pulleys are the idler pulleys due to the fact that they are fixedly mounted with respect to an idler shaft 40 joumaled in side frames of the developer housing 42.

The uppermost pulleys are mounted on shaft 38 which is journaled in the machine housing and driven by a convenient source of power within the machine as motor M-l. This motor rotates the shaft 38 to rotate the pulleys 26 which, in turn, drive the belts 22 and buckets 20 in its path of movement. As the buckets move through the sump in the direction as indicated by the arrow, they will load themselves with developer in the sump. As the motor continues to drive in a continuous cycle of operation, the developer is conveyed upwardly at a slight angle with respect to the vertical toward the upper pulleys 24 for being deposited in the input chute 32.

Located on the upper shaft 38 between the idler pulleys 34 is the roller member 46 mounted on the shaft 38 for rotation therewith. This member is preferably formed of a sofi: resilient material which will not with the materials of the toner or carrier with whrcli i t ii contacted. Polyurethane foam has been found desirable. And, inasmuch as it is not desired that the roller retain any of the developer particles, it is constructed of the closed cell polyurethane foam.

As the individual buckets move upwardly and are then moved from their straight line path of movement by passing around the upper reaches of the idler pulleys, the buckets sequentially tip, dumping the developer material toward the input chute and over the intermediate close cell polyurethane roller rotating therewith. If this roller were not employed a large quantity of the developer would fall between the pulleys back into the sump and the total conveying efficiency of the system would be greatly reduced.

As the bucket moved around the drive pulleys at the same linear speed as the surface of the roller, the internal edge of the bucket contacting the roller will slightly deform the roller to make a closed, moving seal. This prohibits virtually all developer from taking any path of travel but over the rollers and into the entrance chute above the development zone.

Although the developer is deposited to the input chute in a slightly sporadic fashion due to the sequential tipping of the buckets, this is not detrimental since the development zone is fed from developer which forms a continual head or backup of the developer which is metered to the development zone at a proper rate of flow as indicated by the input geometry and size of the opening above the development zone.

While the instant invention as to its objects and advantages has been described as carried out in a specificembodiment thereof, it is not intended to be so limited but is intended to be protected broadly within the scope of the appended claims.

What is claimed is:

l. A bucket conveyor assembly for transporting particulate material including upper and lower pairs of pulleys and a pair of belts,

each belt being trained over one upper and one lower pulley,

elongated buckets secured at each end to a belt for movement with said belts and pulleys between a lower loading position and an upper unloading position,

means to drive said belts and the buckets secured thereto along a path of movement whereby the buckets are transported over said upper pulleys, and

resilient roller means mounted between the upper pulleys and being arranged to be deformed by said buckets moving in contact therewith to provide a seal therebetween to prohibit the dropping of particulate material between said pulleys.

2. The assembly asset forth in claim 1 wherein said deformable roller means is formed of a polyurethane elastomeric material.

3. The assembly as set forth in claim 1 wherein said resilient roller is arranged to move at the same rate as said pulleys. 

1. A bucket conveyor assembly for transporting particulate material including upper and lower pairs of pulleys and a pair of belts, each belt being trained over one upper and one lower pulley, elongated buckets secured at each end to a belt for movement with said belts and pulleys between a lower loading position and an upper unloading position, means to drive said belts and the buckets secured thereto along a path of movement whereby the buckets are transported over said upper pulleys, and resilient roller means mounted between the upper pulleys and being arranged to be deformed by said buckets moving in contact therewith to provide a seal therebetween to prohibit the dropping of particulate material between said pulleys.
 2. The assembly as set forth in claim 1 wherein said deformable roller means is formed of a polyurethane elastomeric material.
 3. The assembly as set forth in claim 1 wherein said resilient roller is arranged to move at the same rate as said pulleys. 